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Yayın Tractable supply chain production planning, modeling nonlinear lead time and quality of service constraints(Elsevier Ltd, 2007) Anlı, Osman Murat; Caramanis, Michael C.; Paschalidis, Ioannis Ch.This paper addresses the task of coordinated planning of a supply chain (SC). Work in process (WIP) in each facility participating in the SC, finished goods inventory, and backlogged demand costs are minimized over the planning horizon. In addition to the usual modeling of linear material flow balance equations, variable lead time (LT) requirements, resulting from the increasing incremental WIP as a facility's utilization increases, are also modeled. In recognition of the emerging significance of quality of service (QoS), that is control of stockout probability to meet demand on time, maximum stockout probability constraints are also modeled explicitly. Lead time and QoS modeling require incorporation of nonlinear constraints in the production planning optimization process. The quantification of these nonlinear constraints must capture statistics of the stochastic behaviour of production facilities revealed during a time scale for shorter than the customary weekly time scale of the planning process. The apparent computational complexity of planning production against variable LT and QoS constraints has long resulted in MRP-based scheduling practices that ignore the LT and QoS constraints has long resulted in MRP-based scheduling practices that ignore the LT and QoS impact to the plan's detriment. The computational complexity challenge was overcome by proposing and adopting a time-scale decomposition approach to production planning where short-time-scale stochastic dynamics are modeled in multiple facility-specific subproblems that receive tentative targets from a deterministic master problem and return statistics to it. A converging and scalable iterative methodology is implemented, providing evidence that significantly lower cost production plans are achievable in a computationally tractable manner.Yayın Optimal project duration for resource leveling(Elsevier Science BV, 2018-04-16) Atan, Sabri Tankut; Eren, ElifResource leveling is important in project management as resource fluctuations are costly and undesired. Typically, schedules with better resource profiles are obtained by shifting the activities within their float times using the schedule of fixed duration found by Critical Path Method. However, if the project duration can be extended, it is plausible to find a schedule with enhanced resource leveling since a longer duration allows for more float time for all activities. In this work, we relax the assumption of fixed durations in resource leveling formulations and investigate what the minimal project duration for the best leveled schedule should be. We provide mixed-integer linear models for several leveling objectives including the Release and Rehire metric. We show that not all metrics used for leveling under fixed durations may be appropriate when the project duration becomes a decision variable. Optimal solutions from smaller problems are used to find the magnitude of the extension needed and benefits obtained thereby. Since the problem is a NP-hard problem for which exact solutions cannot be obtained for large networks in reasonable time, we provide a greedy heuristic to be used with the Release and Rehire metric. Using an iterative framework, we also test the performance of a state-of-the-art heuristic algorithm from the literature on our problem. Computational experiments indicate that the more the number of resources is increased, the less leveling benefits are gained from extending the project. The optimal project durations and extension benefits can also be significantly different for different metrics.Yayın Action readiness and mindset for IT offshoring(Emerald Group Publishing Limited, 2010) Aydın, Mehmet Nafiz; de Groot, Jeroen; van Hillegersberg, JosPurpose: The paper aims to examine the degree of changes in action readiness and mindset for the IT offshore outsourcing (offshoring) practice of a number of leading finance and insurance organisations. In particular, the article investigates the action readiness (the state, condition or quality of being ready) and mindset (habits, opinions or perceptions which affect a person's attitudes) of organisations for IT offshoring. Design/methodology/approach: The research method applied has explorative research characteristics and consisted of two phases. The first phase included conducting interviews with project managers of 12 organisations in home and offshore countries and the second phase was concerned with an in-depth analysis of projects in three organisations. By adopting a process research approach, the research takes into account the dynamics of IT offshoring projects in terms of five essential aspects, i.e. the way of working culture, method use, IT activities, IT governance, and knowledge sharing. Findings: The findings indicate that to a greater extent organisations have realised readiness for method use and the mindset for IT activities, and that the overall improvements regarding these aspects have been modest in the last two years. On the other hand, the mindset for dealing with cultural difference has increased while readiness for flexible working, tracking of requirements change, efficient division of work, and systematic communication is still inadequate. Research limitations/implications: As the findings are concerned with a small sample and particular industries, they are limited in nature. More research is needed to update the findings in other industries with a larger sample. This would help in achieving stronger external validity. Practical implications: The model used in this research can help organisations in identifying how well they are prepared for or have improved IT offshoring practice in terms of five essential aspects. Based on the degree of readiness and mindset at hand, they can make use of the findings related to particular aspects. In this respect, the findings may provide valuable insights for practitioners. Originality/value: Most IT offshoring studies employ a variance research strategy, by which cause-effect relationships among dependent, independent, and mediating factors essential to the subject matter are studied. As an alternative to this strategy, this research adopts a process research approach, which is concerned with the dynamics of IT offshoring practice, which takes into account the emergent and on-the-fly nature of IT projects. Such dynamics are examined in terms of two conceptual levels, i.e. action readiness (ability, condition of being readiness) and mindset (opinions, perceptions). These levels, which are often employed as a separate focus in existing studies, are found to be useful in closing the gap between action readiness and mindset for IT offshoring.
